Influence of Introduced Reindeer on the Vegetation of South Georgia: Results From a Long-Term Exclusion Experiment

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Abstract
(1) The sub-Antarctic island of South Georgia has a species-poor vascular flora that is not adapted to grazing by vertebrates. Consequently, reindeer(Rangifer tarandus L.) introduced to different areas on the island in 1911 and 1925 have had a serious impact on the vegetation. (2) Experimental exclosures and cages were established in various plant communities in 1973-74, and changes in floristic composition and vegetation cover have been recorded for 12 years. (3) Recovery of vegetation in exclosures showed that the native grass Poa flabellata and the dwarf shrub Acaena magellanica increased in cover in response to removal of grazing pressure. In contrast, the introduced grass Poa annua and, to a lesser extent, the moss Polytrichum and bare ground decreased in cover in response to exclusion. Other species and various communities including macrolichens, mossbanks, oligotrophic mire and eutrophic mire showed little change. (4) The experiment demonstrated that several of the important components of the vegetation affected by reindeer can rapidly regain their former abundance when grazing pressure is removed entirely. The major exception is macrolichens, notably of the genus Cladonia, which will probably take several decades to recover. (5) Although grazing does not apparently threaten the survival of any native plant species, an active management policy to eradicate reindeer would be necessary to allow native vegetation to re-establish natural communities.